Development of a methodology for the extraction of BSIM3v3.2.2 parameters of Ge-channel MOSFETs and estimation of analog circuit performance

We have developed an algorithm which utilizes model equations for MOSFETs to extract BSIM3v3.2.2 MOSFET model parameters of Ge-channel transistors. The model represents the entire transfer characteristics from sub-threshold to strong inversion regions and the output characteristics from linear to saturation regions thus capturing all the operating bias conditions of gate to source voltage V_GS and drain to source voltage V_DS. For extraction of various BSIM parameters, the model equations are fitted with reported experimental characteristics, and some with TCAD simulation data of Ge MOSFETs for various geometrical dimensions over a wide range of bias conditions. The algorithm used for extracting BSIM3V3.2.2 parameters by fitting BSIM3v3.2.2 model equations with experimental or simulation data is written in MATLAB code. The extracted BSIM model parameters are employed in ADS circuit simulator to reproduce the transfer characteristics of Ge MOSFETs with the same channel length and channel width of 80 nm for both high and low body bias conditions. The characteristics obtained from ADS match well with those obtained from TCAD simulation using SILVACOATLAS thereby ensuring the accuracy of our extraction methodology. The extracted set of BSIM3V3.2.2 parameters is used to generate transfer and output characteristics of Ge channel pMOSFETs at channel length of 70 nm. The extracted value of threshold voltage, bulk mobility and saturation velocity are −0.2 V, 0.18 m²/V.s and 1.2 × 10⁶ m/s, respectively. Our study reveals that various device parameters such as transconductance, intrinsic voltage gain, and cut-off frequency show a maximum value of 677 μS/μm, 2.7, and 63 GHz, respectively.